There are a number of fluid-flow, particularly liquid-flow, regulating devices for the control of the rate of flow of a gravity-fed or gravity-assisted fluid-delivery system. Such flow-control devices and regulators are particularly useful for delivery of liquids, such as intravenous fluids or other fluids, in medical applications. Typical fluid-flow regulators and adjustable fluid-flow regulators are described, for example, in U.S. Pat. No. 3,929,157, issued Dec. 30, 1975, and U.S. Pat. No. 4,096,879, issued June 27, 1978. The devices described therein, while effective, are often quite complicated in structure and require the production of a number of integrally molded parts and the hand-production and hand-assembly of such parts.
For example, the adjustable fluid-flow regulator device of U.S. Pat. No. 4,096,879 comprises a pair of upper and lower chambers, each chamber having a double-acting float valve therein for opening and closing an inlet and an outlet in each chamber, with the chambers being separate and connected by a flexible tube. The flow rate of the regulator device as described is dependent upon the spacing between the fluid level in the upper chamber and the metering orifice and upon the crosssectional size of the metering orifice in the lower chamber fluid inlet. This adjustable flow-regulator device, although useful, is not easily and simply manufactured and is quite complicated in both construction and operation.